Conventional fuel rails for fuel-injected internal combustion engines comprise sockets which are spaced apart along the fuel rail's length and into which the fuel injectors are inserted. The fuel injectors are retained in fluid-tight relation to the fuel rail by suitable sealing and retention means. The typical fuel injector has an elongated shape and is customarily arranged on the fuel rail such that the long dimension of the injector is transverse to the long dimension of the fuel rail. As a consequence of this arrangement, the envelope that is occupied by the fuel rail assembly in the engine compartment of an automotive vehicle will have an extent transverse to the fuel rail that is determined by the long dimension of the fuel injector. Accordingly, a reduction in the extent to which a fuel injector projects transversely of the fuel rail will be beneficial in reducing the envelope occupied by the fuel rail assembly, and this benefit will accrue to the advantage of automotive vehicle designers insofar as styling and packaging considerations are concerned.
The patent application that has been referenced above relates to a fuel rail that contains a novel fuel injector configuration which allows for certain reductions in the size of the envelope that is occupied by the fuel rail assembly on an internal combustion engine, particularly reductions in the extent to which the fuel injectors project transversely of the fuel rail. More specifically, the fuel rail may comprise a circular cylindrical-walled tube within which the fuel injectors are essentially entirely disposed so that the transverse dimension of the fuel rail assembly at the location of a fuel injector is essentially that of the O.D. of the tube. The fuel injectors are mounted on a carrier to form a sub-assembly that is assembled into the tube by endwise insertion. The electrical leads for the fuel injectors run along the carrier to a receptacle that is at one lengthwise end of the completed fuel rail assembly. The injectors' tip ends from which liquid fuel is injected are seated in a sealed manner in holes in the sidewall of the tube.
The fuel injectors themselves are unique. Rather than having a solenoid, an armature, a needle, and a seat coaxially arranged along the length of the fuel injector, as in conventional fuel injectors, the fuel injector of the referenced application has a magnetic circuit that encircles a spherical valve element. This sphere is resiliently urged by a cantilever spring blade toward closure of a hole that is circumscribed by a frusto-conical seat. The sphere-encircling magnetic circuit may be considered to comprise four sides. The armature and the solenoid are disposed at two opposite sides. The stator has a U-shape whose base passes through the solenoid and whose legs form the remaining two sides. The armature is a bar of magnetically permeable material whose midpoint acts on the sphere. When the solenoid is not energized, working gaps exist between the ends of the bar and the distal ends of the stator's legs, and when the solenoid is energized, the magnetic flux attracts the bar to reduce these working gaps. As a result, the bar pushes the sphere out of concentricity with the seat to cause the hole to open and pass for injection from the injector's tip end the pressurized liquid fuel that has been supplied to the injector via the interior of the fuel rail tube. When the solenoid is de-energized, the cantilever spring pushes the sphere back to concentricity with the seat, and the resultant hole closure terminates the injection. The fuel injector is well-suited for miniaturization to fit within a fuel rail and is an efficient and economical use of parts and materials.
The invention of this division and continuation-in-part patent application relates to features of the fuel rail assembly and its method of manufacture. The fuel rail assembly comprises an elongated carrier that contains spaced apart cavities in which the fuel injectors are respectively disposed. The combination of carrier and fuel injectors forms a sub-assembly which is disposed internally of a tube by inserting the sub-assembly endwise into the tube. The tube may be either a separate tube that is itself ultimately attached to the engine, or a hole in the engine manifold. The carrier also contains electric circuitry for operating the fuel injectors, and includes electrical terminals for making electrical circuit connection to a remotely located engine management computer which delivers principal command signals to the fuel rail assembly for operating the fuel injectors. The carrier-mounted electric circuitry also includes its own microprocessor, a calibration PROM (programmable read only memory, fuel injector drivers, and related auxiliary electronic circuit devices. These further electronic circuit components provide for the fuel rail assembly to be electronically calibrated for dynamic flow throughout the entire dynamic operating range.
The inclusion of such electronic circuitry in the fuel rail assembly confers a number of substantial benefits. Electronic calibration provides improved accuracy because electronic devices can be calibrated with greater precision than can mechanical devices, and because calibration can be conducted for the entire dynamic range by use of a correction table, as opposed to the single fixed test point mechanical calibration that has been the practice up to now. By having a broader range of calibration, it is possible that the fabrication of mechanical parts can be conducted with less strict tolerances, thereby saving on mechanical fabrication costs, while the fuel rail assembly will ultimately obtain better accuracy over the dynamic range by calibrating the self-contained electronics. The usual ability for electronic calibration to be performed more rapidly than mechanical calibration will save on the time required for making a fuel rail assembly. Hence, a given calibration machine will be able to process more assemblies per unit time, and for mass-production purposes, a fewer number of such machines, and hence a lower capital investment, will be the result. By having the calibration electronics, the injector drivers and the injectors in a single package, the manufacturer will be better able to match the fuel rail to the principal command signals issued to the fuel rail from the engine management computer. In the embodiments of the invention that will be illustrated herein, the self-contained electronics are immersed in the liquid fuel within the fuel rail, and in comparison to prior designs which package the electronics with the engine management computer remote from the fuel rail assembly, this allows heat dissipated by the electronics, particularly heat from the drivers, to be rejected to the liquid fuel, and it also removes a source of electrical noise from the immediate vicinity of the engine management computer. The fuel rail assembly may also include associated sensors, such as a pressure sensor for sensing pressure of liquid fuel within the fuel rail assembly and a fuel mixture sensor for sensing the composition of the fuel, such as a methanol sensor for sensing the relative proportions of gasoline and methanol in the liquid fuel. Thus is it possible to fabricate a common fuel rail assembly that can be electronically customized and adapted to accommodate a multitude of varying uses.
Further features, advantages, and benefits of the invention, along with those already mentioned, will be seen in the ensuing description and claims, which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.